The present invention relates to systems for terminating underground utility locator or trace wires. The invention relates more particularly to a method and device for terminating an underground utility locator wire that reduces the risk of signal bleed or transfer, protects the locator wire from damage, and reduces the amount of labor required for installation.
It is known in the art to utilize trace or locator wires to mark the location of underground utility constructions such as water pipes, gas lines, and the like. The purpose of such locator wires is to provide a way to locate buried utility constructions, particularly in the case of non-electrically conductive utility constructions, by detecting a signal passed through the locator wire. Current utility construction practices include placement of an insulated locator wire in a trench containing, for example, a waterline or gas main. Commonly, non-electric grade insulated 12 gauge or 14 gauge wire is utilized. By connecting a line location transmitting device to the locator wire, a line location receiver may detect the signal induced, allowing easy location of an underground system such as a water line or gas main from the surface without need for random digging. This method is utilized by many utility companies to facilitate construction and/or excavation activities, i.e. to allow construction and/or repair work without fear of rupturing existing water lines or gas mains.
A locator wire must be terminated in some fashion. Current industry practices include connecting the locator wire to existing structures, such as, for example, fire hydrants or gate valves. Another common practice is to extend the locator wire above ground and directly attach it to a utility component. Yet another currently employed practice is to connect the locator wire to a short section of electrical ground rod and embed the rod in a concrete pad.
Disadvantageously, all of the above methods allow some level of signal bleed and/or signal transfer from the locator wire to adjacent utility constructions. Such signal bleed and/or transfer can result in difficulty in locating the buried utility construction. It is known that any signal bleed or transfer at or near the point at which a line location transmitter is connected to the locator wire will greatly reduce the distance at which the induced signal can be detected. In addition, the practice of extending the bare locator wire above ground exposes the wire to damage from, e.g., use of the utility component to which the wire is connected, mowing operations, or the like, and reduces the effective life of the locator wire. The practice of attaching the wire to a section of electrical ground rod and embedding the rod in concrete is labor intensive in the installation, and also allows signal bleed or transfer. Such signal bleed/transfer at or near the point where the line location transmitting device is connected to the trace wire greatly reduces the distance at which the induced signal may be detected.
Accordingly, there is need in the art for a method and apparatus for terminating locator wires to provide long-term usage with minimal loss of signal upon operation. There is further a need in the art for a method and apparatus for terminating locator or trace wires requiring less labor for installation than current systems.
In accordance with the purposes of the present invention as described herein, the present invention provides a device and method for terminating a locator wire, designed for use with any conventional locator wire. The present invention may be adapted for use near any known utility construction requiring locator wire, such as water lines, gas mains or lines, and the like. In one aspect, the present invention provides a device for terminating a locator wire for locating an underground utility conveyance, comprising a sheath for electrically isolating said locator wire from ground, and an electrically conductive terminal placed in electrical communication with the locator wire. Advantageously, the device of the present invention allows termination of a locator wire without need for attaching the wire to an existing utility, thereby minimizing signal bleed or transfer from the locator wire to the utility. Additionally, as will be described herein the device of the present invention eliminates the need to bring the locator wire aboveground for termination, thereby minimizing the risk of damage to the wire from incidental operations, such as mowing. Specifically, the present invention allows termination of a buried locator wire without need for bringing the wire aboveground.
In one embodiment, the sheath for electrically isolating the locator wire may be constructed as a unitary piece. In yet another embodiment, the sheath may comprise at least two interlocking members for capturing a portion of an existing structure, such as a utility construction, therebetween. Typically, the sheath will be fabricated from an electrically insulating material. Any suitable electrically insulating material may be selected, such as for example concrete, cement, plastic, polymers, rubber, or combinations thereof. The sheath may include a metallic outer rim, such as for example cast iron, to minimize risk of damage to the remaining components. However, it will be appreciated that in the case of a metallic component to the sheath, the electrically conductive terminal will be electrically isolated from any metallic component of the sheath to prevent signal bleed.
The sheath may include a recess for receiving the electrically conductive terminal, thereby maintaining the tip of the terminal below the top surface of the sheath and providing protection from incidental damage. Typically, the recess may include a cap or lid for covering the recess with the terminal received therein, thereby further protecting the terminal from incidental damage, inclement weather, and the like.
The electrically conductive terminal includes a body fabricated of an electrically conductive material, typically an electrically conductive metal such as copper, steel, galvanized steel, or aluminum. It will be appreciated that the body of the terminal may be of any desired shape, depending upon the specific installation requirements. The terminal may be placed in electrical communication with the locator wire by any conventional means, such as by use of a clamp, by wrapping the locator wire around the terminal, by soldering, or the like. The terminal may also include an integral wire tail for placing the terminal in electrical communication with the locator wire. The locator wire may be attached to the wire tail by any desired means, such as a conventional underground wire splice kit.
The terminal may be fabricated of a single metal, a combination of metals, or any suitable electrically conductive alloy. Any suitable metal possessing a high level of conductivity, but resistant to corrosion, may be used. In one embodiment of the present invention, the terminal may comprise an inner core and an outer coating wherein the inner core is fabricated from an easily detectable metal, and the outer coating is fabricated from a conductive metal. In a presently preferred embodiment, the inner core is fabricated of steel and the outer core is fabricated of copper. It will be appreciated that fabricating the terminal partially from an easily detectable metal such as steel facilitates location of the terminal in instances where the terminal is completely buried, for example using a conventional metal detector.
In another aspect of the present invention, a method for electrically isolating a locator wire for locating an underground utility conveyance is provided comprising the steps of positioning the locator wire in substantial alignment with a buried underground utility conveyance, placing an end of the locator wire in electrical communication with an electrically conductive terminal as described above, and electrically isolating the terminal, and thereby the attached locator wire, with an electrically insulating sheath as described above. As noted above, the locator wire may be directly attached to the terminal, or may be attached by means of an integral wire tail extending from the body of the terminal.
In still yet another aspect of the present invention, a method for locating an underground utility conveyance such as a water main or gas main is provided, comprising the steps of positioning an electrically conductive locator wire in substantial alignment with the underground utility conveyance, placing an end of the locator wire in electrical communication with an electrically conductive terminal, surrounding the electrically conductive terminal with an electrically insulating sheath, applying a suitable signal to the electrically conductive terminal, and therethrough to the electrically conductive locator wire using a suitable signal transmitter, and detecting the signal, and thereby the location of the locator wire and utility conveyance, with a detector. Numerous suitable signal transmitter and detector systems are known in the art for conductive tracing of a buried utility conveyance, such as generators for generating an electromagnetic signal, for generating a signal of a particular radio-frequency, and the like. In the case of a signal of a particular radio-frequency, a suitable signal is one applied at a frequency of from about 60 Hz to about 85 KHz.
In contrast to conventional methods of terminating a locator wire, such as directly attaching the wire to a utility construction or to a grounding rod (both of which allow signal bleed and expose the locator wire, risking damage thereto), the present invention allows a completely insulated, electrically isolated connection which is physically protected from damage and minimizes the risk of signal bleed or transfer to adjacent utilities. Other objects and applications of the present invention will become apparent to those skilled in this art from the, following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of the modes currently best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.